Physicists find weak spots in ceramic/graphe…

Physicists find weak spots in ceramic/graphene composites

Physicists and materials scientists from Peter the Great St.Petersburg Polytechnic University (SPbPU) analyzed the structures in nanomaterials made of ceramic and graphene plates, in which cracks appear most frequently. The results of the first trial of the model, that describes this regularity, were published in the Mechanics of Materials Journal. This model will help in creation of crack-resistant materials. The research was supported by the Russian Science Foundation grant.

Graphene is the lightest and strongest carbon composite. Moreover, it has a very high electrical conductivity. Because of these characteristics graphene is often included in the composition of new ceramic-based materials. Ceramics are resistant to high temperatures, and, if carbon modifications are added, the composites become multifunctional. In the future they can be used in production of flexible electronic devices, sensors, in construction and aviation.

It is known from many experimental studies of such composites that their mechanical characteristics are set by the graphene proportion in the composition and by the size of graphene plates allocated in the ceramic matrix. For example, in the case of low graphene concentration, high crack resistance was achieved with the help of long plates. However, in one of the recent experiments of synthesis of materials from alumina ceramics and graphene, the opposite effect was shown: as the plates were bigger, the crack resistance was weaker. The researchers from Saint Petersburg have developed a theoretical model that explains this paradox.

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Using a scanning tunneling microscope to mak…

Using a scanning tunneling microscope to make origami structures out of graphene

A team of researchers from the Chinese Academy of Sciences, Vanderbilt University and the University of Maryland has created origami-like structures made out of graphene using scanning tunneling microscopy. In their paper published in the journal Science, the group explains how they achieved this feat and possible applications.

For several decades, scientists have sought to fold sheets of graphene in controllable ways. While some managed to fold sheets of graphene, they were either not able to do it in a controlled way, or they had to pretreat the graphene to make it bend in certain places. Scientists believe that if graphene sheets could be manipulated controllably, the resulting materials would have desired properties—one example would be bending it at a “magic angle” to make it superconductive. Others hope to develop smaller processors than can be made using silicon. In this new effort, the researchers claim to have found a way to fold nanoislands of graphene controllably.

The first step involved creating the nanoislands of graphene. The researchers fired hydrogen ions at sheets of graphite for 10 cycles, a process that took 10 hours. This produced high-quality graphene that could stand up to manipulation without breaking or bending in unreliable ways. After that, the team used a scanning tunneling microscope (STM) to grab parts of the nanoislands and then to hold onto them as the sheet was folded, much like a piece of paper. They note that it took some expertise on the part of the person controlling the STM to manipulate the sheets accurately.

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Regular

Synthesizing single-crystalline hexagonal graphene quantum dots

A KAIST team has designed a novel strategy for synthesizing single-crystalline graphene quantum dots, which emit stable blue light. The research team confirmed that a display made of their synthesized graphene quantum dots successfully emitted blue light with stable electric pressure, reportedly resolving the long-standing challenges of blue light emission in manufactured displays. The study, led by Professor O Ok Park in the Department of Chemical and Biological Engineering, was featured online in Nano Letterson July 5.

Graphene has gained increased attention as a next-generation material for its heat and electrical conductivity as well as its transparency. However, single and multi-layered graphene have characteristics of a conductor so that it is difficult to apply into semiconductor. Only when downsized to the nanoscale, semiconductor’s distinct feature of bandgap will be exhibited to emit the light in the graphene. This illuminating featuring of dot is referred to as a graphene quantum dot.

Conventionally, single-crystalline graphene has been fabricated by chemical vapor deposition (CVD) on copper or nickel thin films, or by peeling graphite physically and chemically. However, graphene made via chemical vapor deposition is mainly used for large-surface transparent electrodes. Meanwhile, graphene made by chemical and physical peeling carries uneven size defects.

The research team explained that their graphene quantum dots exhibited a very stable single-phase reaction when they mixed amine and acetic acid with an aqueous solution of glucose. Then, they synthesized single-crystalline graphene quantum dots from the self-assembly of the reaction intermediate. In the course of fabrication, the team developed a new separation method at a low-temperature precipitation, which led to successfully creating a homogeneous nucleation of graphene quantum dots via a single-phase reaction.

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A novel graphene-matrix-assisted stabilizati…

A novel graphene-matrix-assisted stabilization method will help 2-D materials become a part of quantum computers

Scientists from Russia and Japan found a way of stabilizing two-dimensional copper oxide (CuO) materials by using graphene. Along with being the main candidates for spintronics applications, these materials may be used in forthcoming quantum computers. The results of the study were published in The Journal of Physical Chemistry C.

The family of 2-D materials has recently been joined by a new class, the monolayers of oxides and carbides of transition metals, which have been the subject of extensive theoretical and experimental research. These new materials are of great interest to scientists due to their unusual rectangular atomic structure and chemical and physical properties, and in particular, a unique 2-D rectangular copper oxide cell which does not exist in crystalline (3-D) form, as opposed to most of the 2-D materials, whether well-known or discovered lately, which have a lattice similar to that of their crystalline (3-D) counterparts. The main hindrance for practical use of monolayers is their low stability.

A group of scientists from MISiS, the Institute of Biochemical Physics of RAS (IBCP), Skoltech, and the National Institute for Materials Science in Japan (NIMS) discovered 2-D copper oxide materials with an unusual crystal structure inside the two-layer graphene matrix using experimental methods.

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Similarities in the insulating states of twi…

Similarities in the insulating states of twisted bilayer graphene and cuprates

In recent decades, enormous research efforts have been expended on the exploration and explanation of high-temperature (high-Tc) superconductors, a class of materials exhibiting zero resistance at particularly high temperatures. Now a team of scientists from the United States, Germany and Japan explains in Nature how the electronic structure in twisted bilayer graphene influences the emergence of the insulating state in these systems, which is the precursor to superconductivity in high-Tc materials.

Finding a material which superconducts at room temperature would lead to a technological revolution, alleviate the energy crisis (as nowadays most energy is lost on the way from generation to usage) and boost computing performance to an entirely new level. However, despite the progress made in understanding these systems, a full theoretical description is still elusive, leaving our search for room temperature superconductivity mainly serendipitous.

In a major scientific breakthrough in 2018, twisted bilayer graphene (TBLG) was shown to exhibit phases of matter akin to those of a certain class of high-Tc superconducting materials—the so-called high-Tc cuprates. This represents a novel inroad via a much cleaner and more controllable experimental setup.

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Atomically precise bottom-up synthesis of π-…

Atomically precise bottom-up synthesis of π-extended [5] triangulene

Chemists have predicted zigzag-edged triangular graphene molecules (ZTGMs) to host ferromagnetically coupled edge states, with net spin scaling with the molecular size. Such molecules can afford large spin tunability, which is crucial to engineer next-generation molecular spintronics. However, the scalable synthesis of large ZTGMs and the direct observation of their edge states are a long-standing challenge due to the high chemical instability of the molecule.

In a recent report on Science Advances, Jie Su and colleagues at the interdisciplinary departments of chemistry, advanced 2-D materials, physics and engineering developed bottom-up synthesis of π-extended [5]triangulene with atomic precision using surface-assisted cyclodehydrogenationof a molecular precursor on metallic surfaces. Using atomic force microscopy(AFM) measurements, Su et al. resolved the ZTGM-like skeleton containing 15 fused benzene rings. Then, using scanning tunneling spectroscopy (STM) measurements they revealed the edge-localized electronic states. Coupled with supporting density functional theory calculations, Su et al. showed that [5]triangulenes synthesized on gold [Au (111)] retained an open-shell π-conjugated character with magnetic ground states.

In synthetic organic chemistry, when triangular motifs are clipped along the zigzag orientation of graphene, scientists can create an entire family of zigzag-edged triangular graphene molecules. Such molecules are predicted to have multiple, unpaired π-electrons (Pi-electrons) and high-spin ground states with large net spin that scaled linearly with the number of carbon atoms of the zigzag edges. Scientists therefore consider ZTGMs as promising candidates for molecular spintronic devices.

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Experiments explore the mysteries of ‘…

Experiments explore the mysteries of ‘magic’ angle superconductors

In spring 2018, the surprising discovery of superconductivity in a new material set the scientific community abuzz. Built by layering one carbon sheet atop another and twisting the top one at a “magic” angle, the material enabled electrons to flow without resistance, a trait that could dramatically boost energy efficient power transmission and usher in a host of new technologies.

Now, new experiments conducted at Princeton give hints at how this material—known as magic-angle twisted graphene—gives rise to superconductivity. In this week’s issue of the journal Nature, Princeton researchers provide firm evidence that the superconducting behavior arises from strong interactions between electrons, yielding insights into the rules that electrons follow when superconductivity emerges.

“This is one of the hottest topics in physics,” said Ali Yazdani, the Class of 1909 Professor of Physics and senior author of the study. “This is a material that is incredibly simple, just two sheets of carbon that you stick one on top of the other, and it shows superconductivity.”

Exactly how superconductivity arises is a mystery that laboratories around the world are racing to solve. The field even has a name, “twistronics.”

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Physicists discover new quantum trick for gr…

Physicists discover new quantum trick for graphene: magnetism

Sometimes the best discoveries happen when scientists least expect it. While trying to replicate another team’s finding, Stanford physicists recently stumbled upon a novel form of magnetism, predicted but never seen before, that is generated when two honeycomb-shaped lattices of carbon are carefully stacked and rotated to a special angle.

The authors suggest the magnetism, called orbital ferromagnetism, could prove useful for certain applications, such as quantum computing. The group describes their finding in the July 25 issue of the journal Science.

“We were not aiming for magnetism. We found what may be the most exciting thing in my career to date through partially targeted and partially accidental exploration,” said study leader David Goldhaber-Gordon, a professor of physics at Stanford’s School of Humanities and Sciences. “Our discovery shows that the most interesting things turn out to be surprises sometimes.”

The Stanford researchers inadvertently made their discovery while trying to reproduce a finding that was sending shockwaves through the physics community. In early 2018, Pablo Jarillo-Herrero’s group at MIT announced that they had coaxed a stack of two subtly misaligned sheets of carbon atoms—twisted bilayer graphene—to conduct electricity without resistance, a property known as superconductivity.

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A graphene superconductor that plays more than…

A graphene superconductor that plays more than one tune: Researchers at Berkeley Lab have developed a tiny toolkit for scientists to study exotic quantum physics

Researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a graphene device that’s thinner than a human hair but has a depth of special traits. It easily switches from a superconducting material that conducts electricity without losing any energy, to an insulator that resists the flow of electric current, and back again to a superconductor – all with a simple flip of a switch. Their findings were reported today in the journal Nature.

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“Usually, when someone wants to study how electrons interact with each other in a superconducting quantum phase versus an insulating phase, they would need to look at different materials. With our system, you can study both the superconductivity phase and the insulating phase in one place,” said Guorui Chen, the study’s lead author and a postdoctoral researcher in the lab of Feng Wang, who led the study. Wang, a faculty scientist in Berkeley Lab’s Materials Sciences Division, is also a UC Berkeley physics professor.

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Left out to dry: A more efficient way to har…

Left out to dry: A more efficient way to harvest algae biomass

A team at the University of Tsukuba introduced a new procedure of harvesting energy and organic molecules from algae using nanoporous graphene and porous graphene foams. By developing a reusable system that can evaporate water at high rate without the need for centrifugation or squeezing. This research has a great potential for the application of producing cleaner, cheaper, and more efficient biofuels, vitamins, and chemicals.

In the fight against global climate change, algae biomass is a very exciting field of research, because they are photosynthetic microorganisms that convert light energyfrom the sun into energy-rich biomolecules. When algae are grown and harvested on an industrial scale, these molecules can be converted into a wide array of important compounds, including biofuel, medicines, omega-3 dietary supplements, and many other valuable bio-products. Algae are also able to absorb carbon dioxide as they grow, switching from traditional fossil fuels to biofuels holds the promise of slashing net greenhouse gas emissions. However, micro-algae cultures consist primarily of water at low solid content (0.05—1.0 wt%) and harvesting the organic material due to solid-liquid separation techniques usually requires multiple dehydration steps.

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